Some opiate drugs have molecular structures so similar to endorphins that they mimic endorphin's euphoric effects in the brain, making these opiate drugs which kind of molecule?.

What layer of the atmosphere is directly above the troposphere?

Which statement is usually true about the relationship between activation energy and reaction rates? low activation energy barriers result in low rates. high activation energy barriers result in low rates. low activation energy barriers result in no reaction. high activation energy barriers result in no reaction.

Compare and contrast refraction of light and sound will give brainliest